The present invention relates to processes and apparatus for the application of fluids, being more particularly concerned with fluid distribution mechanisms for coating materials on surfaces being hereinafter generically referred to as "sheets" or "sheet means" or the like, for such purposes as, for example, hot melt adhesive, solvent type pressure-sensitive adhesive, resins, plastic, or other fluid materials.
Fluid distribution mechanisms for depositing fluid coatings in predetermined patterns (including intermittent configurations) upon surfaces such as sheets and the like, have been employed through the years in a wide variety of applications. In the illustrative example of adhesive coatings and the like, dispensers involving shuttered openings and nozzles have been employed as described, for example, in U.S. Pat. No. 3,174,689, issued Mar. 23, 1965 to the applicant D. B. McIntyre herein. Such fluid distribution systems have sometimes employed hot melt dispenser apparatus, for example, where the adhesive material and the like is converted from solid to molten form and continuously distributed along predetermined patterns, with or without a bumper spot, for such uses as the adhesive coating of papers and other materials. Apparatus of this nature may, for example, be of the form described in U.S. Pat. No. 3,323,510, issued June 6, 1967 to said D. B. McIntyre.
The philosophy underlying such and related techniques has principally resided in the forcing of the adhesive or other fluid out of nozzle structures and upon moving sheets and the like at controlled instants of time and for controlled intermittent periods of time with the aid of metered units such as, for example, the Type 1BUP2 marketed by Acumeter Laboratories, Inc., Newton Lower Falls, Massachusetts, or other well-known types of fluid metering mechanism. A further example of such an intermittent expanded-nozzle construction and system for the intermittent application of such coatings and deposits upon moving sheets or articles is described in U.S. Pat. No. 3,595,204, issued Jul. 27, 1971 to said D. B. McIntyre and F. S. McIntyre. Clearly, however, other types of fluid application and distribution apparatus may be and have been employed for related purposes.
There are occasions, however, where either the fineness of the dots, lines, or other patterns of this fluid coating to be deposited, or the rate of high speed of the sheet or other material, imposes too stringent conditions upon metered distribution nozzles and the like. For example, with a web or sheet moving at an approximately 1000 feet per minute rate or 16 feet per second, the estimated time for an application of adhesive one-eighth inch long in the direction of web travel, would require an on-time of three-fourth of one millisecond. The fastest practical electrical devices, such as solenoid valves, however, are capable of cycling at rates of the order of a cycle in about 30 milliseconds, more or less, making the use of such techniques for applying adhesive and the like thus unfeasible for the purposes of the present invention.